1. Field of the Invention
The fire damper which is the subject of this invention is particularly useful in conjunction with an electrostatic precipitator. Such precipitators are useful in cleaning air in industrial applications prior to returning it to the atmosphere. Such electronic air cleaners have particular application in the removal of very fine, particles in the neighborhood of 1 micron and below, although such units will handle virtually any airborne particles existing in the air stream being treated. Such a precipitator will provide a clean atmosphere while at the same time, in some instances, effecting recovery of materials which may be recycled.
The electrostatic precipitators for which the fire damper of this invention has been specifically designed are quite sensitive to elevated temperatures and fire and may readily be destroyed when exposed to them. In view of the fact that such precipitators are fairly expensive, it is desirable to protect them from exposure to elevated temperatures and fire. This is something which must be done quickly and positively. The precipitators are located so as to receive air issuing from the process area of a plant so at to clean same before discharging it to atmosphere or recirculating it. Merely to block the process air from the precipitator in time of elevated temperatures as caused by fire, however, is really not enough; not only should the air be diverted from the precipitator in times of fire and the like, but also it should be so directed as to prevent any possible flashback into the process.
2. Description of the Prior Art
Prior means to protect electrostatic precipitators and the like from fire and elevated temperatures have been varied. In some instances nothing was provided. One of the earlier protecting means included an arrangement for flooding the precipitator with water. Another arrangement involved the use of two groups of shutter-like members of the "venetian blind" type, motorized, one group to block the flow of process air to the precipitator and another group to divert such air elsewhere. Some of the prior art arrangements utilized fusable links which, upon actuation, would permit a spring to pull shut a door in the path of air moving towards the precipitator. Fuses and the like, however, often act too slowly and mechanical means such as springs and the like sometimes fail to work at all or also act too slowly. An object of the invention, therefore, is to eliminate as much as possible in the way of mechanical means between the sensing of the emergency condition and actuation of the damper.
As indicated, electrostatic precipitators to which the fire damper of this invention may be employed, are known in the art. An ionizer may be utilized to produce an electrostatic field so as to charge the particles exposed to it. These charged particles are then passed through a collecting cell comprised of charged and grounded plates so as to pick up the charged particles or contaminants.
No search of the United States Patent art has been conducted in conjunction with the fire damper of this invention nor are there any patents known as directed to, for example, the types of control units above indicated as being a part of the prior art. This is not to say, however, that there are no such patents.
There are a number of United States patents known as relating to electronic air cleaners. Some of these are as follows:
U.S. Pat. Nos. 1,697,316--HORNY:1,758,404--LABBE:2,347,709--PENNEY:
2,470,356--MACKENZIE:2,476,248--MACKENZIE:2,490,979--PALMER:
2,535,696--RICHARDSON:2,542,262--RICHARDSON:2,642,952--LANDGRAF:
2,667,941--EKSTROM:2,789,656--RICHARDSON:2,869,678--ROBERTS:
3,540,191--HERMAN:3,581,470--AITKENHEAD:3,605,915--GATELY:
3,707,828--BURNEY:3,778,970--SWIMMER: and 3,788,041--GAYLORD.
It is known that there are a number of other United States Patents relating to electronic air cleaners and, as indicated above, it is probable that there are United States Letters Patents directed to means for protecting them from elevated temperatures and fire, although patents specific to such protecting devices are not included above because not specifically known. No assertion is made, therefore, that the patents which are listed are indeed representative of the best art in this area, let alone representative of the best art known to the fire damper as such.